ksmbd: add validation in smb2 negotiate

This patch add validation to check request buffer check in smb2
negotiate and fix null pointer deferencing oops in smb3_preauth_hash_rsp()
that found from manual test.

Cc: Tom Talpey <tom@talpey.com>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Ralph Böhme <slow@samba.org>
Cc: Hyunchul Lee <hyc.lee@gmail.com>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Ralph Boehme <slow@samba.org>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 27 insertions, 5 deletions

diff --git a/fs/ksmbd/smb_common.c b/fs/ksmbd/smb_common.c
index 5901b2884c60..db8042a173d0 100644
--- a/fs/ksmbd/smb_common.c
+++ b/fs/ksmbd/smb_common.c
@@ -169,10 +169,12 @@ static bool supported_protocol(int idx)
 		idx <= server_conf.max_protocol);
 }
 
-static char *next_dialect(char *dialect, int *next_off)
+static char *next_dialect(char *dialect, int *next_off, int bcount)
 {
 	dialect = dialect + *next_off;
-	*next_off = strlen(dialect);
+	*next_off = strnlen(dialect, bcount);
+	if (dialect[*next_off] != '\0')
+		return NULL;
 	return dialect;
 }
 
@@ -187,7 +189,9 @@ static int ksmbd_lookup_dialect_by_name(char *cli_dialects, __le16 byte_count)
 		dialect = cli_dialects;
 		bcount = le16_to_cpu(byte_count);
 		do {
-			dialect = next_dialect(dialect, &next);
+			dialect = next_dialect(dialect, &next, bcount);
+			if (!dialect)
+				break;
 			ksmbd_debug(SMB, "client requested dialect %s\n",
 				    dialect);
 			if (!strcmp(dialect, smb1_protos[i].name)) {
@@ -235,13 +239,22 @@ int ksmbd_lookup_dialect_by_id(__le16 *cli_dialects, __le16 dialects_count)
 
 static int ksmbd_negotiate_smb_dialect(void *buf)
 {
-	__le32 proto;
+	int smb_buf_length = get_rfc1002_len(buf);
+	__le32 proto = ((struct smb2_hdr *)buf)->ProtocolId;
 
-	proto = ((struct smb2_hdr *)buf)->ProtocolId;
 	if (proto == SMB2_PROTO_NUMBER) {
 		struct smb2_negotiate_req *req;
+		int smb2_neg_size =
+			offsetof(struct smb2_negotiate_req, Dialects) - 4;
 
 		req = (struct smb2_negotiate_req *)buf;
+		if (smb2_neg_size > smb_buf_length)
+			goto err_out;
+
+		if (smb2_neg_size + le16_to_cpu(req->DialectCount) * sizeof(__le16) >
+		    smb_buf_length)
+			goto err_out;
+
 		return ksmbd_lookup_dialect_by_id(req->Dialects,
 						  req->DialectCount);
 	}
@@ -251,10 +264,19 @@ static int ksmbd_negotiate_smb_dialect(void *buf)
 		struct smb_negotiate_req *req;
 
 		req = (struct smb_negotiate_req *)buf;
+		if (le16_to_cpu(req->ByteCount) < 2)
+			goto err_out;
+
+		if (offsetof(struct smb_negotiate_req, DialectsArray) - 4 +
+			le16_to_cpu(req->ByteCount) > smb_buf_length) {
+			goto err_out;
+		}
+
 		return ksmbd_lookup_dialect_by_name(req->DialectsArray,
 						    req->ByteCount);
 	}
 
+err_out:
 	return BAD_PROT_ID;
 }